1,721,024 research outputs found
Aspects of Large N Analysis for Yang-Mills-Higgs and Matrix Models
No full textThesis submitted for the degree of "Doctor Philosophiae", academic year 1995/199
Three-dimensional large N monopole gas
No full textWe study here the large N limit in the presence of magnetic monopoles in the Yang-Mills/Higgs model in three dimensions. The physics in the limit depends strongly on the distribution of eigenvalues of the Higgs field in the vacuum, and we propose a particular, nondegenerate configuration. It minimizes the free energy at the moment of symmetry breaking. Given this, the magnetic monopoles show a wide hierarchy of masses, and some are vanishing as 1/N. The dilute gas picture, then, provides an interesting framework for the large N analysis
SO(10) fermion masses from rank-1 structures of flavour
No full textWe describe a predictive model of SU(3) flavour in the context of SO(10) supersymmetric GUT, that can fit all the known fermion properties: masses, mixing angles and CKM phase, at 1σ level. The mechanism is based on the coupling of fermions at GUT scale to three flavour triplet higgses that are able to generate the correct flavour structure. The model predicts exact unification of determinants of Yukawa couplings, that is found in interesting agreement with experimental data. In the neutrino sector it predicts direct and hierarchical neutrinos, together with nonzero θe3. The correct sign of the leptogenesys asymmetry is a further outcome of the numerical analysis
Aspects of Large N Analysis for the Yang-Mills-Higgs Model and Matrix Models
No full textThe first part of this work deals with some new large N ideas for the YMH
model in three dimensions. Needless to say there is a large historical and scientific
background and it is of course difficult to say something really new on these subjects.
Nevertheless some latest ideas on matrix models, subject on which I have worked
in the first part of my period here at SISSA, are a valuable tool and should find
applications in otherwise 'slow' fields. The study of large N model of monopole
gas are not investigated, to our knowledge, for example. This work wants to be a
starting point for this investigation.
Along this analysis we have found many and different problems to think about,
the principal is the reason how the Eguchi Kawai works, an issue that also has not
been completely clarified, despite of the volume of numerical calculations.
After one finds a reliable method for the functional determinant, it will be possible
to draw definite conclusions on the large N monopole gas, which seems promising
some interesting feature, due to the competition of factors which takes place in the
large N limit
STANDARD MODEL AND GRAVITY FROM SPINORS
No full textIt is shown how the Lorentz and standard-model gauge groups can be unified by using algebraic spinors of the standard four-dimensional Clifford algebra, in left–right symmetric fashion. This defines a framework of unification with gravity and generates exactly a standard-model family of fermions, while a Pati–Salam unification group emerges, at the Planck scale, where (chiral) gravity decouples. We show that this low-energy broken phase emerges from the VEV of extended vierbein fields, which at this stage are as- sumed to be dynamically generated from a theory in the fully symmetric phase valid beyond the Planck scale (and whose consistency and dynamics is thus yet to be assessed) pro- viding thus a geometrical and group-theoretical framework for the unification and breaking. At low energy, on the other hand, it is intriguing to find, as a remnant of this unification, new isospin-triplet spin-two particles that may naturally lie at the weak scale, providing a striking signal at the LHC
Magnetic anomaly in UCN trapping: signal for neutron oscillations to parallel world?
No full textPresent experiments do not exclude that the neu- tron n oscillates, with an appreciable probability, into its in- visible degenerate twin from a parallel world, the so-called mirror neutron n′. These oscillations were searched experi- mentally by monitoring the neutron losses in ultra-cold neu- tron traps, where they can be revealed by the magnetic field dependence of n–n′ transition probability. In this work we reanalyze the experimental data acquired by the group of A.P. Serebrov at Institute Laue–Langevin, and find a depen- dence at more than 5σ away from the null hypothesis. This anomaly can be interpreted as oscillation of neutrons to mir- ror neutrons with a timescale of few seconds, in the presence of a mirror magnetic field order 0.1 G at the Earth. This re- sult, if confirmed by future experiments, will have deepest consequences for fundamental particle physics, astrophysics and cosmology
Nucleon-nucleon Bremsstrahlung emission of massive axions
No full textWe consider the problem of axion production by bremsstrahlung emission in a nuclear medium. The usual assumption of a massless axion is replaced by more general hypotheses, so that we can describe the emission process for axions with mass up to a few MeV. We point out that in certain physical situations the contribution from nonzero mass is non-negligible. In particular, in the mechanism for the production of gamma ray bursts via emission of heavy axions the axion mass (ma 1 MeV) is comparable with the temperature of the nuclear medium, and thus can not be disregarded. Looking at our results we find, in fact, a fairly considerable reduction of the axion luminosity in that mechanism
The Dark Matter halo of the Milky Way, AD 2013
Full text linkWe derive the mass model of the Milky Way (MW), crucial for Dark Matter (DM) direct and indirect detection, using recent data and a cored dark matter (DM) halo profile, which is favoured by studies of external galaxies. The method used consists in fitting a spherically symmetric model of the Galaxy with a Burkert DM halo profile to available data: MW terminal velocities in the region inside the solar circle, circular velocity as recently estimated from maser star forming regions at intermediate radii, and velocity dispersions of stellar halo tracers for the outermost Galactic region. The latter are reproduced by integrating the Jeans equation for every modeled mass distribution, and by allowing for different velocity anisotropies for different tracer populations. For comparison we also consider a Navarro-Frenk-White profile. We find that the cored profile is the preferred one, with a shallow central density of ρH ∼ 4 × 107M⊙/kpc3 and a large core radius RH ∼ 10kpc, as observed in external spirals and in agreement with the mass model underlying the Universal Rotation Curve of spirals. We describe also the derived model uncertainties, which are crucially driven by the poorly constrained velocity dispersion anisotropies of halo tracers. The emerging cored DM distribution has implications for the DM annihilation angular profile, which is much less boosted in the Galactic center direction with respect to the case of the standard ΛCDM, NFW profile. Using the derived uncertainties we discuss finally the limitations and prospects to discriminate between cored and cusped DM profile with a possible observed diffuse DM annihilation signal. The present mass model aims to characterize the present-day description of the distribution of matter in our Galaxy, which is needed to frame current crucial issues of Cosmology, Astrophysics and Elementary Particles
Parity from SO(7, 1) and SO(7, 7) gauge symmetries
No full textLeft-Right parity symmetry P can arise from a unified gauge symmetry, involving gravitational interactions. Parity can survive to the symmetry breaking of the gauge group at Planck scale and can be spontaneously broken at lower energies, as in Left-Right symmetric models with P
Fermion masses at intermediate tan(beta): Unification of Yukawa determinants
No full textIn the context of the Grand Unified MSSM, we investigate the fermion mass matrices at GUT scale. We note that from the experimental mass pattern the determinants of the Yukawa matrices at this scale can be unified with good precision. Taking the unification o determinants as an hypothesis, it gives two model independent predictions that in the MSSM turns out to determine an appropriate value for the product mdms and tan β ≃ 7–10 in the favored range. We then review a predictive model of SU(3) flavour in the context of supersymmetric SO(10) that nicely implements this mechanism, while explaining all fermion masses and mixings at 1σ level, including neutrino data
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